The more sexually explicit, and the more the storyline focuses on sex, the better the sales.
Just passing on simple facts here: I have over 30 titles and have been selling eBooks for years. I don’t pay for advertising, so my customers are those using search and browse on Amazon, also flow-on sales from one book to another.
All of my books have erotic content. I categorize them as being X-Rated (about sex) or R-Rated (containing sex). The books that are ABOUT sex outsell the ones that only CONTAIN sex by a country mile – month after month.
I conclude two things from this:
1) Sex is awesome, natural and beautiful.
2) The customer is right.